This invention relates generally to an improved method of and apparatus for drilling oil and gas wells and, more particularly, to a balance system for rotating equipment, such as a drill for drilling wells.
When drilling with a mud motor, reactive torque is a problem. High drilling rates and high weight on the bit causes the mud motor to stall, the bit to stop, and the drill string to rotate in the opposite direction due to torque build-up in the drill string. Reactive and torsional loads on the drill string may also result in mud motor failure. The solution to this problem is taught and claimed in parent application Ser. No. 09/606,607, now U.S. Pat. No. 6,378,626.
Another common problem in the well drilling art is that of imbalance of the rotating member. An imbalance may occur when clay or other material adheres to the rotating member, thereby placing more weight on one side of the rotating member than the other. An imbalance may also occur during normal operations due to the slant of the well, and other reasons. The present invention is directed solving this problem of imbalance in the rotating member, and is particularly adapted to the imbalance that may occur in a drill string.
The apparatus of the invention shown and described in parent application Ser. No. 09/606,607, now U.S. Pat. No. 6,378,626 includes a drill bit, a fluid powered motor connected to the bit for rotating the bit, and an underreamer above the bit to increase the diameter of the well bore. That invention further includes a gear box positioned between the bit and the underreamer for transmitting the reactive torque of the fluid powered motor to the underreamer to rotate the underreamer in a direction opposite that of the bit. In that way, the torque rotating on the bit is substantially the same as the torque rotating the underreamer, thereby creating a balanced torque drilling system.
The present invention further includes structure to balance the rotating members. The embodiment described below relates generally to rotating members, and is applied in the specific example to a drill bit. Balancing the rotating members such as the bit, stabilizer and underreamer is accomplished by grooved circular races that contain a portion of high density small pellets in an oil/TEFLON fluid medium. The pellets do not fill the grooves so that centrifugal force produced by the rotating tool causes balancing and increases mud motor life by decreasing bearing failure.
These and other objects, advantages, and features of this invention will be apparent to those skilled in the art from this specification including the attached drawings, and appended claims.